Set voltages and amperage for devices

In summary: Resistivity is important because it affects how well an inductor can resonate and how efficiently power is transferred.
  • #1
user111_23
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I see some devices have voltage and amperage ratings on them. Are these just the recommended operating conditions? Or are they something else?

Also, how do engineers determine how much voltage and current does a circuit need?

I see ratings for resistivity as well. Why does resistivity matter in, say, a vacuum cleaner?
 
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  • #2
Circuits involving solid state devices have voltage requirements that are determined by the manufacture of the device. Often these voltages are industry standards.

Examine any of the wall warts that you may have for your various electronic devices. You will find that they have a specified input voltage, like 120VAC, or now frequently they say 230 or 120VAC. You never want to exceed the stated input voltage this is a very quick way to destroy your wall wart. Fortunately this is not easy to do since anything other then these voltages is uncommon. Be careful about taking US products to Europe.

Each wall wart also will specify a output voltage and current. These need to be compared to the input voltage and current as stated on your electronic device. It is risky business to connect a voltage higher then a device is rated for. So if your boom box is rated at 6V input connecting a 12V output wall wart could very well destroy your boom box. Once you have matched the voltage check the current ratings on both the wall wart and the device. The wall wart current rating must be equal to or greater then the current rating of the device. Connecting a lower current wall wart can damage your wall wart.
 
  • #3
user111_23 said:
I see some devices have voltage and amperage ratings on them. Are these just the recommended operating conditions? Or are they something else?

These are for ideal conditions but shouldn't vary too much. Here is Australia our electrical supply system specifies 230V although the service rules allow +10% to -2% for supply to the house. This means you could have between 225V and 253V depending on how far from the transformer you are. Let's look at an example to see how much difference it makes.

An easy one is a hot water system rated at 3.6kW 230V to work out current 3600/230= 15.65A
next work out the resistance of the heating coil R = V/I 230/15.65 = 14.7 ohms
now we can work out how many amps the same hot water system would draw for different possible voltages. I=E/R

225V 225/14.7= 15.3A
253V 253/14.7= 17.2A

As you can see the same device can have its current vary by about 10% depending on voltage. Nothing really to worry about but I hope it answers your question. The plate ratings are for ideal circumstances.

user111_23 said:
I see ratings for resistivity as well. Why does resistivity matter in, say, a vacuum cleaner?
Haven't really seen that except for larger motors. You can test the winding resistance to see if there are any shorts etc... Anyone else?
 

1. What is the difference between voltage and amperage?

Voltage refers to the potential difference between two points in an electrical circuit, while amperage is the measure of the flow of electric charge through a circuit. In simpler terms, voltage is the force that pushes electrons through a circuit, while amperage is the amount of electrons that flow through the circuit.

2. How do I determine the appropriate voltage and amperage for a device?

The appropriate voltage and amperage for a device can usually be found in the device's user manual or on its label. It is important to match the voltage and amperage requirements of the device with the power source to avoid damaging the device or causing a safety hazard.

3. Can I use a higher voltage or amperage than what is recommended for a device?

No, it is not recommended to use a higher voltage or amperage than what is recommended for a device. This can cause the device to overheat, malfunction, or even catch fire. Always use the recommended voltage and amperage for the device.

4. What happens if I use a lower voltage or amperage than what is recommended for a device?

If you use a lower voltage or amperage than what is recommended for a device, it may not function properly or at all. This is because the device is not receiving enough power to operate as intended. It is important to use the recommended voltage and amperage for the device to ensure its proper functioning.

5. How do I adjust the voltage and amperage for a device?

The voltage and amperage for a device can be adjusted through the use of a power supply or transformer. These tools allow you to regulate the amount of voltage and amperage being supplied to the device. It is important to follow the device's instructions and use caution when adjusting the voltage and amperage to avoid damaging the device.

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